1. Field of the Invention
The present invention relates generally to an optical pickup. In particular, it relates to a support structure for the optical pickup allowing two-dimensioned adjustment.
2. Description of the Prior Art
An optical pickup is arranged in a manner so that laser light emitted for reading information is converged into a spotlight beam incident on a recording track formed on an information recording surface of a recording medium, such as a disk. The optical pickup then detects changes of intensity of light reflected from the information recording surface of the disk to thereby read out the information recorded on the disk. To this end, it is necessary to reliably converge the incident laser light on the recording track even in the presence of planar undulations of the recording surface due to surface warping of the recording disk. The optical pickup is therefore arranged so that a focusing servo operation is performed so as to finely move an objective lens converging the laser light in a direction perpendicular to the recording surface to thereby achieve adjustment in the focus. Further, it is necessary to make the converged laser light always correctly trace the recording track even when the recording track is eccentric. The optical pickup is therefore arranged so that a tracking servo operation is performed so as to finely move the objective lens converging the laser light perpendicularly to the recording track in the plane of the recording surface.
Such an optical pickup as described above is well known and is disclosed in Japanese Utility Model Unexamined Publication No. 62-1332191. The optical pickup disclosed in this publication is shown in FIGS. 1(A) and 1(B). An objective lens 1 for irradiating a recording surface of a recording medium (not shown) with a spotlight beam is fixed to one open-end side of a cylindrical holder 2. The holder 2 is open at both its opposite ends. A focusing coil 3 is wound on the outer circumferential surface of the cylindrical holder 2, and tracking coils 5a and 5b are fixed on the focusing coil 3. The focusing coil 3 is oriented so that the central axis of the focusing coil 3 is parallel with the optical axis of the objective lens 1. On the other hand, the tracking coils 5a and 5b are fixed on an outer circumferential surface of the focusing coil 3 so that each of the central axes of the tracking coils 5a and 5b is perpendicular to the optical axis of the objective lens 1.
The holder 2 on which the focusing coil 3, the tracking coils 5a and 5b. and the objective lens 1 are fixed is supported on the free ends of four flexible cantilever supports 6 extending in the direction perpendicular to the optical axis of the objective lens 1. This optical axis extends along the direction of an arrow F in the drawing. The fixed ends of the cantilever supports 6, on the contrary, are supported on a mount 7. The mount 7 is fixed by a screw 11 to an outside yoke 10a integrally formed with a base 8 of the optical pickup. The fixed ends of the plate-like cantilever supports 6 are fit into slits 7a formed in a side of the mount 7 and fixed thereto with an adhesive. Since the four cantilever supports 6 are flexible, the holder 2 is movable relative to the base 8 in the direction of the optical axis of the objective lens 1, that is, in the direction of the arrow F. The holder 6 is also movable relative to the base 8 in the direction perpendicular to the optical axis of the objective lens 1 in parallel to the surface of the recording disk, that is, in the direction of an arrow T in the drawing. The base 8 is fixed to a carriage which moves radially with respect to the recording disk.
In addition to the outside yokes 10a and 10b. inside yokes 12a and 12b are integrally formed with the base 8 in positions between the holder 2 and the outside yokes 10a and 10b. Magnets 13a and 13b are attached on the respective surfaces of the outside yokes 10a and 10b facing the inside yokes 12a and 12b with predetermined gaps 15 between the magnets 13a, 13b and the inside yokes 12a, 12b. The base 8, the outside yokes 10a and 10b, and the inside yokes 12a and 12b are composed of a magnetic material. Two magnetic circuits are constituted by the base 8, the outside yokes 10a and 10b the inside yokes 12a and 12b, and the magnets 13a and 13b, with the above-mentioned gaps 15 acting as magnetic gap 15.
The focusing coil 3 and the tracking coils 5a and 5b are partly located within the magnetic gaps 15 so that those coils can be interlinked with magnetic flux produced in the magnetic produced in the magnetic gap 15. As a result, the objective lens 1, which is an optical element, can be driven longitudinally together with the holder 2 in the direction of the arrow F by making a current flow in the focusing coil 3. As a further result, the objective lens 1 can be driven transversely together with the holder 2 in the direction of the arrow T by making a current flow in the tracking coils 5a and 5b.
In the foregoing conventional pickup, however, there has been a disadvantage in that it is necessary to provide the mount 7 solely for the purpose of supporting the fixed ends of the cantilever supports members. Also, the screw 11 is required for fixing the mount 7 to the outside yoke 10a. As a result, the pickup is large in size, heavy in weight and high in cost.